The present invention generally relates to an engine cooling system and more particularly, to an engine cooling system which utilizes an engine mounted cooling recovery reservoir for reduced cooling system complexity, and a thermostat which is integrated within the reservoir fill cap, thereby allowing the thermostat to be easily changed and/or removed and allowing the system to be easily filled and serviced.
In order to cool an engine, a vehicle typically circulates a liquid coolant such as water through the engine and through a heat exchanger (e.g., a radiator) which allows the coolant or water to be desirably cooled. Before the vehicle""s engine reaches a certain temperature, the coolant bypasses the heat exchanger and is used to heat the engine components and the vehicle passenger compartment. Particularly, in cold temperatures, the heated water is typically channeled through a heater core, while air is forced through the heater and communicated to the passenger compartment of the vehicle, thereby desirably increasing the temperature of the passenger compartment. Once the temperature of the coolant exceeds a certain level, a xe2x80x9cthermostatxe2x80x9d is actuated and causes the heated coolant to pass through the radiator. The thermostat includes a wax pellet or element that is heated by the water, and which is effective to expand, thereby actuating a valve within the thermostat, and allowing the coolant to pass through the radiator.
During engine xe2x80x9cwarm upxe2x80x9d, the bypass coolant flow circuit is positioned so that coolant flowing through the engine is channeled to the thermostat, which is typically disposed on the xe2x80x9ccold-sidexe2x80x9d of the radiator, and which receives the coolant prior to the coolant passing through the heater core. Because of this positioning, the operation of the thermostat is governed by the temperature gradient across the entire engine cooling system. As a result, the operation of the thermostat is controlled by the bypass flow rather than the flow through the heater core. If coolant flow from the heater circuit is directed onto the thermostat (rather than bypass flow), then gains in heater performance are achieved due to the thermostat control governed by heater circuit demand.
These vehicle heating and cooling systems also require a relatively large amount of hoses or conduits which interconnect the various components of the cooling system such as the radiator, the coolant recovery reservoir, the engine, the heater core, and the thermostat. This network is relatively complex and provides various potential sources for leaks. Furthermore, these prior systems are relatively difficult to fill, due to this large network of hoses and due to restrictions created by the closed thermostat in the coolant flow circuit. Lastly, the placement of the radiator height position relative to engine height position and reservoir height position creates fill issues due to air entrapment resulting from these varying positions.
There is therefore a need for a new and improved engine cooling system which includes a coolant recovery reservoir which is mounted to the engine, which has an integrated thermostat and refill cap, and which greatly reduces the complexity of the system relative to prior systems.
A first non-limiting advantage of the invention is that it provides an engine cooling system which integrates the coolant recovery reservoir as an engine mounted component for reduced cooling system complexity, hose routing simplification, and a reduction in the number of potential leak source connections.
A second non-limiting advantage of the invention is that it integrates a thermostatic control device into the reservoir cap for ease of coolant filling during vehicle assembly and field service. This also allows the thermostat to be replaced manually without the need for service tools or draining of the cooling system.
A third non-limiting advantage of the invention is that it places the coolant recovery reservoir at a high elevation relative to the engine, heater core and radiator, thereby improving cooling system function and simplifying initial vehicle fill and serviceability. Moreover, because the thermostat is integral with the reservoir fill cap, the system may be filled faster, as the thermostat is entirely removed from the system during the fill procedure, thereby eliminating any restriction during system filling.
A fourth non-limiting advantage of the invention is that it allows for both a conventional wax pellet type thermostat design or an electronic thermostat design which may be selectively controlled by the engine control module or microprocessor.
A fifth non-limiting advantage of the invention is that it reroutes vehicle cabin heater coolant to the thermostat for improved vehicle cabin heater performance under cold ambient conditions of engine transitional warm-up.
A sixth non-limiting advantage of the invention is that it utilizes a design which prevents overfilling of the coolant reservoir during service filling.
A seventh non-limiting advantage of the invention is that it allows the coolant recovery reservoir to be installed during engine assembly for improved leak testing and functional testing prior to installation in a vehicle.
An eighth non-limiting advantage of the invention is that it reduces cooling system fluid volume which reduces the overall system weight and cost.
A ninth non-limiting advantage of the invention is that it utilizes a reservoir design which eliminates steam bubbles from the coolant prior to the coolant entering the radiator, thereby improving heat transfer within the radiator.
A tenth non-limiting advantage of the invention is that it provides full control of the coolant bypass circuit for improved engine warm-up and cooling system performance.
An eleventh non-limiting advantage of the present invention is that it provides an electronically controlled thermostat which results in improved overall system performance, such as faster warm-up in cold ambient conditions, reduced high speed restriction, and which allows for the selective programming of the cooling system and variable engine temperature control for improved drivability, performance and optimal emission control.
According to a first aspect of the present invention, an integrated fluid recovery reservoir and thermostat assembly is provided for use within an engine cooling system of the type including an engine, a radiator, coolant and a pump which selectively circulates the coolant through the engine and the radiator. The assembly includes a coolant reservoir housing which is mounted to the engine and which includes at least one inlet port for receiving coolant from the engine and an outlet flow portion which is fluidly coupled to the radiator; a flow control module which is attached to the reservoir housing and which selectively and fluidly communicates with the reservoir housing, with the pump and with the radiator; and a thermostat assembly which is attached to the flow control module, and which cooperates with the flow control module to selectively control the flow of the coolant through the engine cooling system. The thermostat assembly includes a valve which is selectively movable between a first position in which the coolant bypasses the radiator and flows directly from the reservoir housing to the pump, and a second position which causes the coolant to be selectively channeled from the reservoir housing through the radiator prior to being channeled to the pump.
According to a second aspect of the present invention, a method is provided for channeling coolant within an engine cooling system including an engine, a radiator and a pump. The method includes the steps of: providing a coolant reservoir housing; mounting the coolant reservoir housing to the engine; fluidly coupling the coolant reservoir housing to the engine and to the radiator; providing a fill cap for the coolant reservoir housing; integrating a thermostat assembly within the fill cap for selectively channeling the coolant to the radiator; coupling the thermostat assembly to the radiator and the pump; and causing the thermostat assembly to selectively channel the coolant to the radiator based upon the temperature of the coolant.
These and other features, aspects, and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment of the invention and by reference to the following drawings.